Use the cutoff as a constraint, not a pace promise
An ultra cutoff planner converts distance and time into a minimum average pace. That number is only the first layer. Trail surface, climbing, descents, darkness, congestion, mandatory checks and time stopped at aid stations can all make clock pace different from moving pace.
Before entering anything, copy the current organizer's checkpoint table into your notes. Confirm whether each cutoff is an arrival cutoff or a departure cutoff, whether it applies to all waves, and what happens when a checkpoint is missed. Race rules can change; a saved screenshot from last season is not the authority.
Build a checkpoint worksheet
| Checkpoint | Distance | Official cutoff | Planned arrival | Planned departure | Buffer |
|---|---|---|---|---|---|
| Start | 0 | — | — | — | — |
| CP1 | ___ | ___ | ___ | ___ | ___ |
| CP2 | ___ | ___ | ___ | ___ | ___ |
| Finish | ___ | ___ | ___ | ___ | ___ |
Calculate the course average first, then add expected station time separately. For example, six eight-minute stops add 48 minutes even when every moving split matches the plan. The useful output is therefore not one heroic pace; it is a conservative sequence of arrival and departure decisions.
Choose the buffer from rehearsed evidence
Use recent long runs on comparable terrain to estimate:
- sustainable moving pace by terrain type;
- normal station time when bottles, food and kit are organised;
- pace drift after several hours;
- the effect of darkness, heat, cold or altitude;
- where hiking is faster and safer than forcing a run.
Research on 100 km and 100-mile pacing describes slowing and large individual variation across course segments. Those observational results do not create a universal percentage buffer. Build margin from your course and rehearsals, not from someone else's finish.
Rehearse the decisions, not just the arithmetic
Run one long session with a simple checkpoint card. Record actual arrival time, departure time, food and fluid taken, and the reason for any delay. Change one weak link before the next rehearsal. The ultra training hub can anchor the wider build, while the marathon fueling planner can make an intake schedule explicit enough to test.
Do not try to recover lost time with a hard surge. A small deficit early is a planning problem; chasing it at an unsustainable effort can create a larger deficit later.
Stop rules
Cutoff planning never overrides safety. Stop and seek event medical support for confusion, fainting, severe breathing difficulty, chest pain, repeated vomiting, inability to keep fluid down, or an injury that changes normal movement. Follow the organizer's withdrawal and transport procedure.
This tool is a planning aid, not a guarantee of finishing and not medical advice.